The increasing requirements of the electronics industry for printed circuit boards with component parts assembled and mounted thereon has produced an increasing need for visual aid equipment which can be programmed to provide guidance for the assembly operator over a long series of successive assembly steps, during which many different types of component parts are selected sequentially and assembled in predetermined positions on the printed circuit board.
To avoid the time and expense required to prepare written instruction programs, and the unavoidable operator errors and fatigue involved in reading and following such written programs, visual guidance systems have been proposed and several different visual systems have been marketed. RCA Industrial and Automation Systems of Plymouth, Michigan and Video Wire Inc. of Levittown, Pennsylvania have sold a "Parts Caddy Optical Programming System", utilizing bundles of optical fibers whose ends are epoxy-sealed in the holes of an actual printed circuit board, and are successively illuminated by a programmed optical system.
Other manufacturers, such as Contact Systems, Inc. of Danbury, Connecticut in its "SC200 Component Locator", Modern Plant Equipment Company of Southport, Connecticut in its "NP-48 Assembly Station", and Ragen Precision Instruments, Inc. of North Arlington, New Jersey utilize a slide projector placing an arrow on a screen viewed by the operator, immediately above the printed circuit assembly location. Carlton Design, Inc. of Big Flats, New York has marketed Carlton Component Insertion Equipment, backlighting a printed circuit board with selected spots of illumination. The Manix Manufacturing Division of Henry Mann, Inc. of Huntingdon, Pennsylvania sells a "Manix L35 Assembly System" employing a film strip. Several of these programmed visual aids are coordinated with the sequential exposure of selected bins of component parts.
In its U.S. Pat. No. 3,112,354, the Hughes Aircraft Company has disclosed and claimed a printed circuit assembly visual aid system in which the operator views a printed circuit board through a half-silvered mirror in which the operator simultaneously sees an image of an overhead projection screen. A slide projector and changer are employed to project, through a second, overhead mirror, the images of previously prepared photographic slides illustrating the workpiece in each successive step of the assembly operation.
All of these conventional prior art visual aid systems require either the considerable expense of optical fiber bundle arrangements cemented in place to a specimen printed circuit board, or a series of masks or photographic slides whose registration and alignment must necessarily be extremely critical if helpful guidance is to be provided to the operator. These devices easily fall out of alignment, and slide projectors are notoriously poor at registration of successive views, while exhibiting much unnecessary and distracting detail in each view.
For these reasons a simpler and more foolproof visual aid device has long been needed for the visual guidance of assembly operators performing long series of successive assembly or treatment steps on miniature workpieces such as printed circuit boards.